Diffusion Parameters Of Lateral Pterygoid Muscle During Jaw Rest, Opening, And Clenching

Objective To investigate whether occlusal changes affect the diffusion parameters of the lateral muscle.Subjects and Methods Fifteen healthy volunteers underwent diffusion tensor imaging during jaw rest, opening and clenching. All source images were transferred into an AW4.4workstation to obtain the primary(λ1), secondary(k2), and tertiary eigenvalues(X3), average diffusion coefficient(ADC) and fractional anisotropy(FA).Results When the jaw was at the postural position, both λ3and ADC of the SHLP were significant lower than that of IHLP (P<0.001, P=0.031, respectively), and the FA values of the SHLP were higher than that of the IHLP (P<0.001). At the SHLP, jaw opening caused a significant increase in λ2, λ3and ADC and a significant decrease in FA, and the change in λ1was not significant. Meanwhile, during jaw opening, All three eigenvalues and ADC value of the IHLP were significant higher, and FA was significant lower.At the SHLP, jaw closure caused significant increases in ADC. The three eigenvalues were increased by jaw closure, and the change in λ2,λ3were significant. At the IHLP, the change induced by jaw closure were not significant in all three eigenvalues and ADC.Conclusion The changes of diffusion parameters at SHLP and IHLP induced by jaw opening indicate that both SHLP and IHLP plays an important role in jaw opening movements. The changes induced by jaw closure indicate that SHLP enrolls in the jaw closing movement and IHLP was not active in this movement. The diffusion parameters of the lateral pterygoid were sensitive to jaw position, and they reflect the changes of LP muscle fibers during jaw movements. This study provided a foundation of further study of the lateral pterygoid.